Cost–Benefit Analysis of RAP–Sand Blend Applications in Road Construction

Abstract

Generally, the use of reclaimed asphalt pavement (RAP) has been limited to asphalt mixes. Recently, this trend has changed to include using RAP in unbound pavement layers. However, the cost-effectiveness of this application is not well studied. This paper presents a methodology to conduct cost–benefit analyses for using RAP–sand blend in subgrade and subbase layers considering a general process of RAP–sand blend from different sources until it is used in construction. Eight scenarios of RAP–sand blend applications were considered. Each scenario has two pavement sections (control and alternative) and was evaluated using the mechanistic-empirical approach. The benefit of using RAP–sand blend in the alternative section was assessed in terms of saving in asphalt thickness under various equivalent single axle load (ESALs) ranging between 1 and 12 million. Four mixing options were identified, and results for Option 1 (fresh RAP and mixing at site) indicated significant saving ranging between –$ 0.48 and $9.29/m² depending on the scenario of RAP blend utilization. The highest benefit–cost ratios were also achieved with this option. Estimated benefit–cost ratios ranged between 0.58 and 18.64 depending on the scenario and option considered in the analysis, with uneconomic situations associated with Scenario 3. In this analysis, no significant impact was found for ESALs when their values are above 1 million. Generally, the RAP–sand blend is more effective in reducing required asphalt thickness, especially when used as a subgrade or subbase layer below thinner unbound aggregate layers. The significant saving achieved may encourage future implementation of this blend.